The present invention relates generally to receivers, more particularly to channel estimation and compensation in a receiver.
Receivers receive information over communication channels. Communication channels generally serve to allow propagation of data over space or time. Communication channels may be varied. Copper pairs, optical fiber, and wireless communication channels are commonly used as communication channels, although at times any medium may serve as a communication channel.
Preferably the receiver provides received data to subsequent data usage systems with content of the data unchanged by the transmission/reception process. Unfortunately, due to introduction of noise, information received by the receiver may differ from information transmitted, or intended to be transmitted, by the transmitter. Noise may come from a number of sources, including noise associated with the channel over which the data is transmitted. Often, the noise introduced by the channel includes noise of a non-random nature. Accordingly, knowledge of the effect of the communication channel on the received data may therefore be used to adjust the received signal to account for the non-random noise of the channel.
Many communication systems perform a channel estimation process in the receiver so as to estimate the effect of the communication channel on received information. This channel estimate may thereafter be applied to a received signal to at least partially remove noise introduced by the channel. The channel estimate is often determined as an average over many received symbols as each individual symbol may also impacted by random noise in the channel, which may vary from symbol to symbol.
Unfortunately, in some systems only a limited number of received symbols of information are available for use in determining channel estimates, and the limited number of symbols may be insufficient to provide a channel estimate sufficient to avoid receiver degradation.